Publications by authors named "Akihiko Nishimura"

Objective: Adverse Social Determinants of Health (SDoH) are considered major obstacles to effective management of type-2 diabetes. This study aims to quantify the impact of SDoH factors on diabetes management outcomes.

Materials And Methods: We quantified the joint impact of multiple SDoH by applying a self-control case series method-which accounts for confounding by using individuals as their own control-to electronic health record data from an academic health system in Maryland.

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  • This study compares the cardiovascular effectiveness of different second-line antihyperglycemic agents (SGLT2 inhibitors, GLP-1 receptor agonists, DPP-4 inhibitors, and sulfonylureas) in patients with type 2 diabetes and cardiovascular disease.
  • Using data from over 1.4 million patients across multiple databases, the researchers analyzed the risk of major adverse cardiovascular events (MACE) over a follow-up period of several years.
  • Results indicated that SGLT2 inhibitors and GLP-1 receptor agonists had significantly lower risks of MACE compared to DPP-4 inhibitors and sulfonylureas, pointing to their potential superiority as treatment options for
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Use of continuous shrinkage priors - with a "spike" near zero and heavy-tails towards infinity - is an increasingly popular approach to induce sparsity in parameter estimates. When the parameters are only weakly identified by the likelihood, however, the posterior may end up with tails as heavy as the prior, jeopardizing robustness of inference. A natural solution is to "shrink the shoulders" of a shrinkage prior by lightening up its tails beyond a reasonable parameter range, yielding a version of the prior.

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  • The study aimed to evaluate how often kidney failure occurs in patients receiving intravitreal anti-VEGF treatments and to compare the risks associated with three specific drugs: ranibizumab, aflibercept, and bevacizumab.
  • Researchers conducted a retrospective cohort study, analyzing data from 12 databases within the OHDSI network, focusing on patients over 18 with retinal diseases receiving these treatments.
  • Results showed an average incidence of kidney failure of 678 per 100,000 persons, and no significant differences in risk were found among the three anti-VEGF drugs, indicating similar safety profiles regarding kidney health.
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  • * Bacterial community analysis revealed similarities between samples TW1 and TW2, with TW1 being dominated by a thiosulfate-oxidizing bacterium and TW2 by a manganese-oxidizing bacterium, both showing some radiation resistance.
  • * A significant portion of the identified bacterial genera was linked to metal corrosion, indicating that understanding these microbial communities is crucial for the effective decommissioning of damaged nuclear plants.
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  • * The study analyzed data from over 1.4 million patients treated with various second-line diabetes medications, using advanced statistical methods to compare outcomes and risks of heart issues.
  • * Findings indicated that both SGLT2 inhibitors and GLP-1 receptor agonists reduce the risk of cardiovascular events compared to DPP-4 inhibitors and sulfonylureas, but no significant differences were found between SGLT2is and GLP1-RAs themselves regarding heart risks.
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  • Postmarket safety surveillance is crucial for mass vaccination programs, but traditional methods face challenges like multiple testing issues and data biases, leading to the need for improved approaches.
  • The researchers developed a Bayesian surveillance method that utilizes negative control outcomes to reduce bias and offers increased flexibility in analyzing vaccine-related adverse events.
  • Their empirical evaluation, using data from over 360 million patients, showed that this new method significantly outperformed the existing MaxSPRT approach by reducing Type 1 errors and improving estimation accuracy, with all findings made publicly accessible via an R ShinyApp.
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Molecular clock models undergird modern methods of divergence-time estimation. Local clock models propose that the rate of molecular evolution is constant within phylogenetic subtrees. Current local clock inference procedures exhibit one or more weaknesses, namely they achieve limited scalability to trees with large numbers of taxa, impose model misspecification, or require a priori knowledge of the existence and location of clocks.

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  • The study aimed to evaluate the adoption of second-line antihyperglycaemic medications among type 2 diabetes patients using metformin, analyzing data from 10 US and 7 international health databases.
  • A total of 4.8 million participants were included, focusing on the trends in initiating additional diabetes treatments over the years 2011 to 2021.
  • Results showed significant growth in the use of cardioprotective drugs (like GLP-1 receptor agonists and SGLT2 inhibitors) as second-line options, with initiation rates varying widely across countries and databases.
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Inferring dependencies between mixed-type biological traits while accounting for evolutionary relationships between specimens is of great scientific interest yet remains infeasible when trait and specimen counts grow large. The state-of-the-art approach uses a phylogenetic multivariate probit model to accommodate binary and continuous traits via a latent variable framework, and utilizes an efficient bouncy particle sampler (BPS) to tackle the computational bottleneck-integrating many latent variables from a high-dimensional truncated normal distribution. This approach breaks down as the number of specimens grows and fails to reliably characterize conditional dependencies between traits.

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COVID-19 has challenged health systems to learn how to learn. This paper describes the context, methods and challenges for learning to improve COVID-19 care at one academic health center. Challenges to learning include: (1) choosing a right clinical target; (2) designing methods for accurate predictions by borrowing strength from prior patients' experiences; (3) communicating the methodology to clinicians so they understand and trust it; (4) communicating the predictions to the patient at the moment of clinical decision; and (5) continuously evaluating and revising the methods so they adapt to changing patients and clinical demands.

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Post-approval safety surveillance of medical products using observational healthcare data can help identify safety issues beyond those found in pre-approval trials. When testing sequentially as data accrue, maximum sequential probability ratio testing (MaxSPRT) is a common approach to maintaining nominal type 1 error. However, the true type 1 error may still deviate from the specified one because of systematic error due to the observational nature of the analysis.

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In a modern observational study based on healthcare databases, the number of observations and of predictors typically range in the order of 10-10 and of 10-10. Despite the large sample size, data rarely provide sufficient information to reliably estimate such a large number of parameters. Sparse regression techniques provide potential solutions, one notable approach being the Bayesian method based on shrinkage priors.

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  • The study investigates the potential benefits of alpha-1 blockers, typically used for benign prostatic hyperplasia (BPH), in preventing COVID-19 complications like cytokine storms, but finds insufficient real-world evidence to support this theory.* -
  • Researchers utilized large-scale healthcare databases from Spain and the U.S. to analyze over 2 million users of alpha-1 blockers compared to other BPH medications regarding COVID-19 outcomes, employing advanced techniques to ensure accurate results.* -
  • The findings indicated no significant difference in COVID-19 diagnosis, hospitalization, or severe hospitalization risks between alpha-1 blocker users and those using alternative treatments, suggesting a need for further research into effective COVID-19 therapies.*
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Since the beginning of the COVID-19 pandemic, pharmaceutical treatment hypotheses have abounded, each requiring careful evaluation. A randomized controlled trial generally provides the most credible evaluation of a treatment, but the efficiency and effectiveness of the trial depend on the existing evidence supporting the treatment. The researcher must therefore compile a body of evidence justifying the use of time and resources to further investigate a treatment hypothesis in a trial.

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In severe viral pneumonia, including Coronavirus disease 2019 (COVID-19), the viral replication phase is often followed by hyperinflammation, which can lead to acute respiratory distress syndrome, multi-organ failure, and death. We previously demonstrated that alpha-1 adrenergic receptor (⍺-AR) antagonists can prevent hyperinflammation and death in mice. Here, we conducted retrospective analyses in two cohorts of patients with acute respiratory distress (ARD, n = 18,547) and three cohorts with pneumonia (n = 400,907).

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  • The study investigated whether alpha-1 blockers, typically used for treating benign prostate hyperplasia (BPH), can reduce the risk of complications from COVID-19, particularly by blocking cytokine storms.
  • Researchers compared 2.6 million alpha-1 blocker users with 0.46 million users of alternative BPH treatments from electronic health records in Spain and the U.S. between November 2019 and January 2020.
  • The results showed no significant difference in the risks of COVID-19 diagnosis, hospitalization, or need for intensive services between the two groups, highlighting the necessity for additional research on potential therapies for COVID-19.
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In severe viral pneumonia, including Coronavirus disease 2019 (COVID-19), the viral replication phase is often followed by hyperinflammation, which can lead to acute respiratory distress syndrome, multi-organ failure, and death. We previously demonstrated that alpha-1 adrenergic receptor ($\alpha_1$-AR) antagonists can prevent hyperinflammation and death in mice. Here, we conducted retrospective analyses in two cohorts of patients with acute respiratory distress (ARD, n=18,547) and three cohorts with pneumonia (n=400,907).

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Calculation of the log-likelihood stands as the computational bottleneck for many statistical phylogenetic algorithms. Even worse is its gradient evaluation, often used to target regions of high probability. Order O(N)-dimensional gradient calculations based on the standard pruning algorithm require O(N2) operations, where N is the number of sampled molecular sequences.

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Prior information often takes the form of parameter constraints. Bayesian methods include such information through prior distributions having constrained support. By using posterior sampling algorithms, one can quantify uncertainty without relying on asymptotic approximations.

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